Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.atnf.csiro.au/research/LVmeeting/magsys_pres/ahughes_MagCloudsWorkshop.pdf Дата изменения: Sun Aug 5 03:55:46 2007 Дата индексирования: Sun Dec 23 16:57:18 2007 Кодировка: Поисковые слова: molecular cloud

Atomic and Molecular Gas in the LMC

Annie Hughes (Swinburne/ATNF) Tony Wong (UIUC), Juergen Ott (NRAO), Erik Muller (ATNF), Jorge Pineda (Bonn), Yoji Mizuno (Nagoya), Lister Staveley-Smith (UWA), Sarah Maddison (Swinburne)


Molecular Cloud Lifetimes
Evidence for long molecular cloud lifetimes (>10 Myr): H2 formation on grains Milky Way's star formation rate Evidence for short molecular cloud lifetimes (<10 Myr): Association with young stellar content No turbulent driving required Molecular cloud chemistry Molecular cloud morphology


The HI-CO (HI-H2) Connection
Ph = 0.84 (G* )
0.5

v
g

g 0.5

(h* )

Blitz & Rosolowsky 2006 Audit & Hennebelle 2005 Heitsch et al. 2006


Previous Work on HI envelopes
· "Do all molecular clouds have an HI lining?" (Wannier et al. 1983+)

· inner MW giant molecular clouds are associated with HI superclouds (Elmegreen & Elmegreen 1987) · molecular cloud mass approximately equals the associated HI mass (Blitz et al. 1989+)


CO and HI in the LMC

NANTEN

12

CO

Mmo

l

~ 4-7 x 10

7

M

(Fukui ea. 1999)
-1

MHI ~ 4.8 x 10

8

M

(LSS ea. 2003)
-1

Mopra: =35" & v=0.1 km s

ATCA+PKS: =60" & v=1.7 km s


GMC 0517-6752 Preliminary Results

M

mol

~ 3.8 x 105 M (for Galactic XCO)


GMC 0526-6932 Preliminary Results

M

mol

~ 1.6 x 105 M (for Galactic XCO)


3DSlicer (fingers crossed...) Preliminary Results
· GMC 0520-6901 · GMC 0526-6932 · GMC 0517-6752 · GMC 0528-6951 Pink: Blue: Green: Aqua: Grey: CO 70-80K HI 60-70K HI 40-60K HI 10-40K HI

Purple: 80-90K HI


3DSlicer screen shots Preliminary Results


3DSlicer screen shots Preliminary Results


3DSlicer screen shots Preliminary Results


3DSlicer screen shots Preliminary Results


CO and HI Intensity: 3D Preliminary Results comparison
Tb (HI) = в Ts(1-e-)

Tb(HI) (K)


CO and HI Intensity: 2D Preliminary Results comparisons
Galactic PDR models LMC-CO27


CO vs HI for Individual Preliminary Results Clouds*
24um dark 24um warm 24um hot

Evidence against HI accretion?

*this

is preliminary!


Possible Interpretations Preliminary Results
· Opacity effect? · Rapid HI to H conversion? · HI accretion? · Mechanical feedback?
2

Tb (HI) = в Ts(1-e-)


CO and HI Velocity Dispersion
HI moment 2 map

· GMCs not bordered by high v edges · changing ratio of cold/warm HI? · loss of turbulent support?


Average Properties of HI Envelopes
Average HI properties around ~20 GMCs in inner LMC
Physical Normalized


Size of HI Envelopes


Importance of stellar gravity?


Conclusions
· The LMC is a unique laboratory for this kind of analysis · HI and CO peaks are offset (in space): efficient HI to H2 conversion? Role of optical depth vs gas temperature? · GMCs correlated with low HI velocity dispersion: gas getting colder, or losing turbulent support? · HI envelopes: increasing HI brightness & decreasing HI velocity dispersion over ~ 2 x R ·M
HI GMC

approaches M

H2

over similar scales
env:

· Coherent pattern in R

related to stellar bar?


End